The investigators will conduct a phase 1 clinical study of placebo, 200 mg and 400 mg Oltipraz administered to 20 current smokers per group for 12 weeks. Endpoints of dosimetry will include DNA and hemoglobin adducts of benzo(a)pyrene-7,8-diol-9,10-epoxide in bronchoalveolar macrophages from lavage and epithelial cells from biopsy, and blood lymphocytes and oral mucosa cells. Endpoints will also include measurements of oxidation status, phase II enzymes activities, and 4-aminobiphenyl adducts in bladder lining cells. Correlations will be made with GSTM1 genotype. Tolerability and toxicity will be assessed.